As the demand for electricity skyrockets in the United States and the world, government and private industry must uncover and maximize power sources. One of these sources is natural gas.
Origins of methane (CH4) include conversion of organic material by microorganisms (biogenesis), thermal decomposition of buried organic matter (thermogenesis), and deep crustal processes (abiogenesis). Buoyant methane migrates upward through rock pores and fractures and either accumulates under impermeable layers or eventually reaches the surface and dissipates into the atmosphere. Biogenic methane results from the decomposition of organic matter by methanogens, which are methane-producing micro-organisms and which pervade the near surface of the Earth's crust in regions devoid of oxygen, where temperatures do not exceed 97 degrees Celsius (207 degrees Farenheit). Methanogens also live inside the intestines of most animals (people included) and in the cud of ruminants such as cows and sheep, where they aid in the digestion of vegetable matter.
Because the methane generated in the subsurface is less dense than the rocks in which it is produced, it diffuses slowly upward through tiny, interconnected pore spaces and fractures, and it can eventually reach the Earth's surface and dissipate into the atmosphere. In places, however, the diffusion of methane is impeded by impermeable rock layers and gas can become trapped in structures. If enough gas accumulates under these impermeable layers, the structures can be drilled and gas can be extracted for use as an energy source.
For natural gas, the cycle begins at gas wells, where gas is extracted from the ground. After processing, the gas is compressed and distributed through pipelines. To generate electricity, fuels such as oil, coal, natural gas, nuclear, hydroelectric and others must be extracted, processed, transported and converted.
Natural gas can be used to generate electricity in many different ways. Natural gas power plants generating more than a couple of hundred megawatts (1 megawatt=1 MW=1 million watts) use the same technology as coal fired power plants. Natural gas is burned to produce heat, which boils water, creating steam which passes through a turbine to generate electricity. Slightly smaller natural gas power plants can use gas turbines to produce electricity. Gas turbines are similar to jet engines and can convert up to half the energy of the natural gas fuel into electricity.
These power plants produce emissions that can be harmful to the environment, and are subject to regulatory control by local, state and national governments. In the case of natural gas fired electricity plants, these emission include Nitrous Oxides (NOx) and Carbon Monoxide (CO).
One current approach to controlling and monitoring these emissions utilizes a control algorithm and control system, which uses a signal generated from fuel flow transmitters associated with a metering tube orifice. These transmitters are set up in a split-range function; such that the first transmitter measures low gas flows and the second transmitter measures high gas flows, in order to provide accurate flow readings across the full range of gas flow. The transmitters are used to provide readings to a control system, which in turn controls the injection of steam or water into the combustors to meet emissions and operating requirements. The amount of water required is a function of the fuel flow, the fuel type, the ambient humidity and NOx emissions levels required by the relevant regulations. Transmitters of this type tend to drift and require biannual calibration, at a minimum, to stay within acceptable tolerances.
When the transmitters are miscalibrated, or gas condensate collects in a leg of the fuel flow transmitter, an out-of-compliance event can exist and yet not be detected by the current monitoring system, or a false alarm may be generated.
The present invention is particularly suitable for use with the General Electric SPEEDTRONIC™ Mark IV, Mark V, and Mark VI Gas Turbine Control Systems. The SPEEDTRONIC™ Control Systems are computer systems that utilize microprocessors to execute programs to control the operation of the gas turbine using the transmitter data, sensor inputs and instructions from human operators.
While the above device is a fair representation of the current prior art, there remains room for improvement as defined by the currently-claimed invention.